Means for preventing the adherence of molten metal to an object



July 26, @380 B. F. DAVIDSON ET AL 2,125,057

MEANS F'TR PREVENTING THE ADHERENCE OF MOLTEN METAL TO ANOBJECT Filed May 29, 1935 [N VE N T ORS f DAVIDSON and GARE/V66 Filo/ m;

A TTORNEY Patented July 26, 1938 UNITED STATES PATENT OFFICE MEANS FOR PREVENTING THE ADHERENCE F MOLTEN METAL TO AN OBJECT Benjamin F. Davidson Dubuque, Iowa,

and Clarence F. Morse,

assignors to Mergenthaler 3 Claims.

This invention relates to means for preventing the adherence of molten metal to an object, and especially to means for preventing the adherence of molten metal to the plunger rod of 5 machines designed to produce type bars, types,

and like typographical elements.

In the operation of the casting mechanism of such machines, molten metal contained in a socalled metal pot is ejectedtherefrom into a mold by means of a plunger operating in the well of the pot, this plunger being carried at the lower end of a plunger rod, usually made of steel, which extends upwardly through the bath of molten metal and which is connected above the pot to appropriate power devices operating to reciprocate the plunger down and up during each slug casting operation.

During the reciprocation of the plunger, a central section of the actuating plunger rod is momentarily immersed in the bath of molten metal, and in practice it has been found that each time this section is removed from the bath, metal adheres to the upper end thereof and that the metal which thus adheres accumulates and eventually attains such proportions that in the descent of the plunger rod, it strikes the surface of the bath and causes the same to splash. This action not only detracts from the efficiency of the slug casting operation, but in addition, the splashed metal is thrown out upon adjacent parts of the machine and aside from endangering the operators and others who might be near, it necessitates the stopping of the machine and entails a considerable loss of time in removing the splashed metal from the machine parts and in freeing the rod of the accumulated mass of metal.

This accumulation of metal is believed to be due to the fact that the dissipation of heat by radiation and by conduction from the exposed upper end of the rod so reduces its temperature that the motlen metal is chilled as it is immersed therein during the casting operation; and to the further fact that the time this section is immersed is insufficient to raise its temperature sufficiently high to free it of the metal which adheres to it as a result of being so chilled. The metal, however, which adheres to the rod and which is carried below the surface of the bath is J reheated by the bath to temperatures sufficiently high to free it from the rod but the metal which so adheres to that portion of the rod which is in line with the level of the bath when the plunger is in its down position is not carried below the level of the bath, but on the contrary it is carried upwardly into the air where it hardens about the rod.

In accordance with the present invention, the above, as well as other difliculties, are overcome by enveloping at least that portion of the plunger :5 rod which is in line with the level of the bath when the plunger is in its down position within a shield which is so constructed that the molten metal does not adhere thereto as it is alternately carried into and out of contact therewith.

For a clear understanding of the invention, reference may be made to the accompanying drawing. In the drawing, however, the invention is shown merely in preferred form and by way of example, but obviously many changes and vari- 4115 ations may be made therein and in its mode of application which will be comprised within its spirit. It should therefore, be understood that the invention is not limited to any specific form or embodiment, except in so far as such limitai tions are specified in the claims.

Referring to the drawing:

Fig. 1 is an elevational view, partially in section, of certain portions of a casting machine embodying the principles of the present inven-.j225 tion;

Fig. 2 is an enlarged detail view, partially in section, of the plunger, plunger rod andits associated shield; and

Fig. 3 is a View in section, taken along the linec 3-3 of Fig. 2.

In the drawing, I0 designates a metal pot with a well H therein, and having a discharge spout [2 leading from the well and adapted to deliver molten metal into a mold IS. The ejection of. the molten metal from the pot is effected by means of a plunger l5 movable down and up in the well ll and operated by a plunger rod H extending upwardly from the plunger through the bath of molten metal and connected above the lo .pot to suitable actuating mechanism, including a lever l6 adapted to be operated to move the plunger down and up in successive slug casting operations.

In accordance with the present invention the gradual accumulation of metal about the rod I5 before alluded to, is prevented by means of a shield II which surrounds and which is heat insulated from at least that portion of the rod which is in line with the level of the bath when the plunger I4 is in its down position, the shield being made of a thin sheet of aluminum or other suitable metal or alloy having high heat conducting properties to render it highly sensitive to temperature changes. In the present embodi- 55 ment of the invention the heat insulation is obtained by so constructing the central portion of the shield I1, as shown more clearly in Fig. 2, as to provide an air pocket [8 between it and that portion of the rod which it envelopes. If desired, this air pocket may be packed with suitable heat insulating material but in the present embodiment of the invention this is dispensed with and the insulation offered by the confined air in thepocket is relied on alone. The lower end of the shield terminates in a shoulder I9 which fits tightly about the rod to seal the lower end of the air pocket l8 against the inflow of molten metal, and to prevent displacement of the shield, as it is raised and lowered in the bath, the shoulder I9 is fastened to the rod as by means of a pin 20. The upper end of the shield I! likewise terminates in a shoulder 2|v which also fits tightly about the rod to seal the upper end of the air pocket l8 against the infiow of ambient atmosphere. In the present embodiment of the invention the overall length of the shield I1 is such that the lower end thereof remains immersed in the bath when the plunger I4 is in its raised position as indicated by the full lines in Fig. 1, and the upper end thereof remains above the level of the bath when the plunger is in its down position, as indicated by the dotted lines in the same figure.

The lower portion of the shield, being immersed, even when the plunger I4 is in its normal raised position, absorbs heat from the bath as well as from the immersed lower end of the plunger rod 15 and is, therefore, maintained at a temperature substantially the same as the temperature of the bath, but the upper portion of the shield, being exposed to the ambient atmosphere, loses heat by radiation as well as by conduction through the upper shoulder 2| to the rod l5 and is, therefore, at a temperature which gradually decreases from that portion which is in line with the level of the bath and which is at a temperature substantially the same as the temperature of the bath to the upper end thereof. This gradual decrease in temperature, however, is slight, due to the high heat conducting properties of the shield and to the fact that both the heat radiating and heat conducting losses are limited. The heat radiating losses are limited since they are substantially confined to the exposed outer surface of the shield by virtue of the fact that the inner surface of the shield is sealed against the ambient atmosphere and to the further fact that the air confined in the pocket I8 is maintained at elevated temperatures by heat which is radiated from the immersed lower portion of the shield and from the surrounded portion of the rod l5. Also the heat which is lost by conduction is limited since the temperature gradient between the upper shoulder 2| and that portion of the rod IS with which it contacts is slight, and since the heat which is thus lost by conduction is so limited it ispermitted, in the present embodiment of the invention, to simplify the construction of the shield but it is obvious that this loss could be substantially eliminated by the insertion of an insulating member between the shoulder and the rod,

Since this gradual decrease in temperature is slight, the temperature of this portion of the shield is raised to substantially the temperature of the bath as it is brought into contact therewith when the plunger is moved to its down position, this increase in temperature being due primarily to the high degree of response which the shield has to temperature variations and to the fact that as the shield is immersed its heat absorbing area increases and its heat radiating area decreases accordingly. Under these conditions the molten metal is not chilled suificiently to cause it to adhere to the shield as the shield is brought into contact therewith during the reciprocation of the plunger rod.

Having thus described our invention, we claim:

1. In combination, a pot containing a bath of molten metal, a reciprocable plunger rod so positioned in the pot that a section thereof is alternately carried below and above the level of the bath, and a metal shield carried by said rod, insulated from said section by confined air and of such length that the lower end thereof remains immersed in said bath and the upper end thereof remains abovethe level of the bath as the rod is reciprocated.

2. In a typographical machine, the combination of a pot containing a bath of molten metal,

a reciprocable plunger rod so positioned in the pot that a section thereof is alternately carried below and above the level of the bath as the rod reciprocates, and a metal shield carried by the rod and insulated by confined air from that portion of the rod which is in line with the level of the bath when the rod is in its down position, the length of the shield being such that the upper end thereof remains above the level of the bath and the lower end thereof remains below the level of the bath as the rod reciprocates.

3. In a typographical machine, the combination of a pot containing a bath of molten metal, a reciprocable plunger rod positioned in the pot, and a metal shield positioned about the rod for preventing the adherence of molten metal thereto, the upper end of the shield being secured to the rod above the level of the bath when the rod is in its down position, the lower end of the shield being secured to the rod below the level of the bath when the rod is in its up position and that portion of the shield in line with the level of the bath when the rod is in its down position being separated from that portion of the rod about which it is positioned and of such thinness that its temperature is raised to substantially the temperature of the bath as it is brought into contact therewith.

BENJAMIN F. DAVIDSON. CLARENCE F. MORSE. 

